For some the answer is to ship their luggage rather than lug it through the airport and pay the airlines to take it.
Whether this strategy makes financial sense or not obviously depends on how much the airline is charging for luggage.
There are, however, other considerations: the convenience of not having to lug your luggage.
The insurance you can get from a shipping company is probably far superior, since airline insurance excludes practically everything of value.
But numbers? They probably won't work out...unless the luggage is overweight or over-sized.
If your bag weighs more than 50 pounds, most national airlines charge from 50 to $125 each way.
Using UPS ground to ship a 70 pound package from New York to LA would take 4 days and cost about 90 bucks.
So even with overweight bags, shipping doesn't save much.
Bottom line, unless your luggage is really overweight, you're probably not going to save money by shipping it versus checking it.
However, there is the convenience factor to consider, there's also the insurance and then there's the ever important...spite.